Investigation of ulcer disease in Atlantic Salmon

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Ulcer disease is the primary reason for antibiotic usage in aquaculture on the East coast of Canada. In other countries this condition is caused by Moritella viscosa; however, in Canada other bacterial pathogens have been isolated from lesions with and without the isolation of M. viscosa and the lesions occur at much warmer temperatures. Anecdotal reports suggest mortality from this disease is increasing and it is unknown whether this is due to treatment resistance, increased virulence, reduction in host immunity, increased exposure, or a combination of these factors. Identification of risk factors and management strategies for this disease are needed to improve the sustainability of the industry. To date there are no published summaries of the epidemiology of ulcer disease in Canada. This basic information is essential for developing hypotheses on control and prevention strategies. The overall goal of this project is to better understand the epidemiology of ulcer disease on Atlantic salmon fish farms on the East Coast of Canada. Specifically we aim to 1) describe disease outbreaks with respect to specific environmental and husbandry factors at the pen and farm level, and 2) assess antibiotic treatment efficacy for this pathogen over the last 2 years. We will also investigate exposure to a Canadian isolate of M. viscosa under laboratory conditions to determine if we can mimic the field observations associated with ulcer disease. This research will provide a systematic assessment and description of the epidemiology of ulcer disease, which will provide science-based evidence for treatment and prevention strategies. The preliminary findings from this study will be the basis for a larger, collaborative project with the aquaculture industry within the next year to evaluate different control strategies for this disease.